The present invention relates to torque transmitting systems in general, and more particularly to improvements in transmissions for use in the power trains of motor vehicles. Still more particularly, the invention relates to improvements in variable-speed transmissions, such as infinitely variable-speed transmissions, which can be utilized in the power trains of motor vehicles to transmit torque between a prime mover (such as a combustion engine, a hybrid prime mover, a friction clutch or a hydrokinetic torque converter) and the wheels of a motor vehicle. Still more particularly, the invention relates to improvements in transmissions of the type disclosed in commonly owned U.S. Pat. No. 5,169,365 granted Dec. 8, 1992 to Oswald Friedmann for "POWER TRAIN". Transmissions of such character are also known as variators. The disclosure of the U.S. Pat. No. 5,169,365 (as well as of each other patent or patent application mentioned in this specification and being properly incorporable by reference) is incorporated herein by reference.
The transmission which is disclosed in U.S. Pat. No. 5,169,365 comprises two adjustable pulleys or sheaves (hereinafter called sheaves) and an endless flexible device (such as a chain or a belt and hereinafter called chain for short) which is trained over the sheaves to transmit torque from one of the sheaves (such one sheave can be driven by the prime mover of the motor vehicle) to the other sheave. Each sheave comprises an axially fixed first flange and a second flange which is movable axially of the first flange in order to change the intensity of frictional engagement between the chain and the sheaves and/or to change the ratio of the patented transmission.
Transmissions (variators) of the above outlined character are also disclosed in published European patent application Serial No. 0 341 474. European patent No. 0 518 478 discloses sprocket chains which can be utilized as endless torque transmitting devices in transmissions of the type disclosed in U.S. Pat. No. 5,169,365 and/or in published European patent application Serial No. 0 341 474. A satisfactory chain (such as a sprocket chain or any other link conveyor) normally comprises a series of interconnected contact elements which are spaced apart from one another in the longitudinal direction of the chain or conveyor and have end faces adapted to frictionally engage the adjacent surfaces of flanges forming part of the two sheaves to thus transmit torque from the prime mover-driven sheave to the other sheave when the transmission is in actual use.
Since the aforementioned contact elements of the chain are spaced apart from each other in the longitudinal direction of the chain, they engage the adjacent surfaces (normally conical surfaces) on the flanges of each of the two sheaves at timely spaced intervals at a frequency which depends upon the speed of the chain and upon the mutual spacing of neighboring (successive) contact elements from one another. The loci of actual contact between the surfaces of the flanges of the two sheaves on the one hand, and the end portions of the momentarily adjacent contact elements on the other hand, constitute the corners of two pairs of registering polygons. The reliability of frictional engagement between the chain and the sheaves depends upon the areas of contact between the end faces of the contact elements and the adjacent surfaces of the flanges, upon the friction coefficients of such parts, and upon the forces with which the axially movable flanges are urged against the other flanges of the respective sheaves.
It has been found that repeated engagement of successive contact elements of the chain with, and repeated disengagement of such contact elements from, the adjacent surfaces of the two flanges of each sheave is apt to generate pronounced (readily detectable) noise. As a rule, the flanges of the sheaves and the contact elements of the chain are metallic parts which are bound to generate sounds, at least when successive contact elements of the chain are caused to impinge upon the adjacent surfaces of the flanges of one of the sheaves, thereafter upon the surfaces of the flanges of the other sheave, again upon the surfaces of flanges of the one sheave, and so forth.